Originally Posted by Benny8444

The SFO/ORD-HKG flights are very tough upgrades in the UA system as well as IAD-NRT. There is plenty of paid C pax on this route as well as 1Ks in Y. If the other poster is correct that C is getting full chances are slim as I am sure there are quite a few 1Ks on the list who would get the few remaining seats ahead of you.

I would book the lower fare and go for the buy up at checkin.